1. Field of the Invention
This invention relates to a converter for changing first and second given variables, corresponding to the Cartesian coordinates of a vector, into at least one variable corresponding to the angle coordinate of the vector, represented in polar coordinates.
2. Discussion of the Prior Art
A coordinate converter for changing Cartesian vector variables into polar vector variables is needed for various purposes, e.g., for the field-oriented control of a rotating machine. To date, the computing modules available for the processing of vector variables are the vector analyzer and the vector rotator shown in German Pat. No. 1,941,312, FIGS. 5 and 6, restrictively. These computing modules are suited for the processing of rotating and nonrotating vectors. They require relatively elaborate equipment.
FIG. 16 of the brochure, "IC Programmable Multiplier Divider Computation Circuit", by Analog Devices, Norwood, Mass. (USA) shows a coordinate converter which makes it possible to compute, from a first and a second given variable, a1 and a2, respectively, which correspond to the Cartesian coordinates of a vector, the magnitude a of this vector. There, the derived magnitude corresponds to the magnitude coordinate of the vector described by polar coordinates. No provision is made for calculating the angle coordinate. This existing coordinate converter comprises an integrated module, designated AD 531, which forms an output variable (a1).sup.2 /c from the first variable a1 and from another variable c. The variable c is furnished by a first adder to which the second variable a2 and the magnitude a are supplied. The magnitude a, in turn, is taken from the output of the coordinate converter via a feedback line. The output variable (a1).sup.2 c of the integrated module is fed to a second adder to which the second variable a2 is also applied. Its output variable is the desired vector magnitude a. It is available at the coordinate converter output for further processing. As already mentioned, this coordinate converter is not suited for furnishing an output variable corresponding to the angle coordinate of the vector. In addition, its function is restricted, in that the sign of the second input variable a2 must be positive only.
It is an object of the present invention to provide a coordinate converter of the kind described at the outset for the processing of a vector which is characterized by its simplicity of circuitry and which provides, therefore, for computation of at least the angle coordinate from the Cartesian coordinates of a given vector.